Cycloaddition Reactions of 1‐Alkyl‐3,4,5‐triphenyl‐1,2‐diphosphacyclopenta‐2,4‐dienes

Abstract

Abstract 1‐Alkyl‐3,4,5‐triphenyl‐1,2‐diphosphacyclopenta‐2,4‐dienes 1 , obtained by alkylation of sodium 1,2‐diphospha‐3,4,5‐triphenylcyclopentadienide, exhibit dual reactivity in cycloaddition reactions: as dienes (with maleic anhydride and maleimide) or as dienophiles (with 2,3‐dimethylbutadiene). Thermolysis of 1 occurs with a [1,5] sigmatropic shift to form a [2+2] cyclodimerization product.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)